The invention relates to the technical field of soft magnetism alloy magnetic powder, in particular to a soft magnetism alloy powder used for a electromagnetic transmission component. The chemical component of the soft magnetism alloy magnetic powder comprises, by mass percentage, Fe(100-Q-R-T-W-X-Y-Z)CoQNiRCuTCrUSiXMYM'Z, M and M' are trace other metal or non-metal elements, wherein M is one or more of metal elements except Fe, Co, Ni, Cu and Cr, M' is one or more of non-metal elements of C, O, N, P, S, B, Q=19-23, R=8-10, T=0.1-0.4, U=0.5-1.9, X=0.1-1.2, Y<=0.2, Z<=0.2, and the balance of Fe. The magnetic powder has ordered / disordered phase-change characteristics, and the phase change temperature range is 530-560 DEG C. The magnetic powder has the advantages that the magnetic induction is high, the magnetic conductivity is high, the coercive force is low and residual magnetism is low, the magnetization intensity and the magnetic force are high under an excitation state, the magneticpowder does not aggregate and the fluidity is good under a demagnetization state. The hardness is high, the friction force is high, and the wear resistant performance is good.